Android控件使用FragmentTabHost，切换Fragment；

大部分APP的主界面都很类似，要么底部导航的，要么就是侧滑菜单，还有底部导航+侧滑菜单的；底部导航实现大概有几种方式：

• TabHost+Fragment
• RadioGroup+Fragment
• FragmentTabHost+Fragment
• BottomNavigator+Fragment

今天说一下FragmentTabHost+Fragment实现方式（布局文件在最下面）：

1、定义一个TabBean，存放每个tab；

public class TabBean {
    private int title; // 文字
    private int icon; // 图标
    private Class fragment; // 对应fragment

    public TabBean(Class fragment, int title, int icon ) {
        this.title = title;
        this.icon = icon;
        this.fragment = fragment;
    }

    public int getTitle() {
        return title;
    }

    public void setTitle(int title) {
        this.title = title;
    }

    public int getIcon() {
        return icon;
    }

    public void setIcon(int icon) {
        this.icon = icon;
    }

    public Class getFragment() {
        return fragment;
    }

    public void setFragment(Class fragment) {
        this.fragment = fragment;
    }
}

2、初始化数据集合

  private List<TabBean> mTabs = null;
    private void initData() {
        mTabs = new ArrayList();
        mTabs.add(new TabBean(HomeFragment.class,R.string.home,R.mipmap.ic_launcher_round));
        mTabs.add(new TabBean(HotFragment.class,R.string.hot,R.mipmap.ic_launcher_round));
        mTabs.add(new TabBean(CategoryFragment.class,R.string.category,R.mipmap.ic_launcher_round));
        mTabs.add(new TabBean(CartFragment.class,R.string.cart,R.mipmap.ic_launcher_round));
        mTabs.add(new TabBean(MineFragment.class,R.string.mine,R.mipmap.ic_launcher_round));
    }

3、实例化控件，设置数据；

    private void initView() {
        mTabHost.setup(this,getSupportFragmentManager(),R.id.flContent);

        for(TabBean tab : mTabs){
            TabHost.TabSpec tabSpec = mTabHost.newTabSpec(getString(tab.getTitle()));
            tabSpec.setIndicator(buildIndicator(tab));
            tabSpec.setContent(new TabHost.TabContentFactory() {
                @Override
                public View createTabContent(String s) {
                    return new View(MainActivity.this);
                }
            });
            mTabHost.addTab(tabSpec,tab.getFragment(),null);
        }

        mTabHost.setCurrentTab(0); //默认选中

        mTabHost.setOnTabChangedListener(new TabHost.OnTabChangeListener() {
            @Override
            public void onTabChanged(String tabTitle) {
                 //修改选中Tab的样式（类似状态选择器）
                TabWidget tabw = mTabHost.getTabWidget();
                for (int i = 0; i < tabw.getChildCount(); i++) {
                    View view = tabw.getChildAt(i);
                    TextView tv = (TextView) view.findViewById(R.id.tab_title);
                    if (i == mTabHost.getCurrentTab()) {
                        tv.setTextColor(getResources().getColor(R.color.colorAccent));
                    } else {
                        tv.setTextColor(getResources().getColor(R.color.textColor));
                    }

                }
            }
        });
    }
    //构建Indicator
    private View buildIndicator(TabBean tab){
        View view = LayoutInflater.from(this).inflate(R.layout.tab_indicator,null);
        ImageView img = (ImageView) view.findViewById(R.id.tab_icon);
        TextView text = (TextView) view.findViewById(R.id.tab_title);
        img.setBackgroundResource(tab.getIcon());
        text.setText(tab.getTitle());
        return  view;
    }

完成了！！！ 下面是布局文件（界面的和tab的）

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <FrameLayout
        android:id="@+id/flContent"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"></FrameLayout>

    <android.support.v4.app.FragmentTabHost
        android:id="@+id/tabHost"
        android:layout_width="match_parent"
        android:layout_height="48dp">
    </android.support.v4.app.FragmentTabHost>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:descendantFocusability="afterDescendants"
    android:paddingBottom="4dp"
    android:paddingTop="6dp">

    <ImageView
        android:id="@+id/tab_icon"
        android:layout_width="22dp"
        android:layout_height="22dp"
        android:layout_centerHorizontal="true"
        tools:ignore="ContentDescription" />

    <TextView
        android:id="@+id/tab_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/tab_icon"
        android:layout_centerHorizontal="true"
        android:clickable="false"
        android:enabled="false"
        android:focusable="false"
        android:gravity="center"
        android:textColor="@color/textColor"
        android:textSize="12sp"
        tools:text="tab" />

</RelativeLayout>

FragmentTabHost这个控件每次切换Fragment，都会走Fragment的onCreateView和onDestroyView方法，多以每次切换都会创建和销毁Fragment实例，下篇文章说一下自定义FragmentTabHost避免重复创建和销毁Fragment实例，让Fragment隐藏hide和显示show；FragmentTabHost切换Fragment时保存状态，避免切换Fragment走onCreateView和onDestroyView方法；